At present, three-dimensional filter bags with tags and tie strings are usually made from a flat web of filter paper on which charges of infusion product are placed. The filter paper is then folded around the charge of infusion product and sealed longitudinally to form a continuous tube enclosing the charges of infusion product.
Next, the tube is sealed crossways at regular intervals and cut crossways at the seals to form individual filter bags.
Normally, in this method, the tags and tie strings are applied after the continuous tube has been completely formed, that is to say, once the charges of product have been placed inside it and the crossways seals have been made.
The tags and tie strings are applied by heat sealers located at operating stations forming part of the filter bag making machine that embodies the method described above. These sealers have inherent drawbacks created by their complex, cumbersome drive mechanisms.
The complexity and bulky size of the sealers are due not only to the fact that a large number of sealers are required but also, and especially, to the fact that the sealers have to work in the space around the filter bags after these have been formed.